Comment on duplicate code for parsing double vlans (iovisor#2107)

Comment on duplicate code for parsing double vlans. I also changed it into a short loop, which I don't think improves (or degrades) the code, but at least makes it clear that the double parsing is intentional. Signed-off-by: Paul Chaignon <[email protected]>
yingtaojuzi · Jan 3, 2019 · f446bd7 · f446bd7
1 parent c8e98d1
commit f446bd7
Showing 1 changed file with 12 additions and 17 deletions.
diff --git a/examples/networking/xdp/xdp_drop_count.py b/examples/networking/xdp/xdp_drop_count.py
@@ -96,23 +96,18 @@ def usage():
 
  h_proto = eth->h_proto;
 
- if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
- struct vlan_hdr *vhdr;
-
- vhdr = data + nh_off;
- nh_off += sizeof(struct vlan_hdr);
- if (data + nh_off > data_end)
- return rc;
- h_proto = vhdr->h_vlan_encapsulated_proto;
- }
- if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
- struct vlan_hdr *vhdr;
-
- vhdr = data + nh_off;
- nh_off += sizeof(struct vlan_hdr);
- if (data + nh_off > data_end)
- return rc;
- h_proto = vhdr->h_vlan_encapsulated_proto;
+ // parse double vlans
+ #pragma unroll
+ for (int i=0; i<2; i++) {
+ if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
+ struct vlan_hdr *vhdr;
+
+ vhdr = data + nh_off;
+ nh_off += sizeof(struct vlan_hdr);
+ if (data + nh_off > data_end)
+ return rc;
+ h_proto = vhdr->h_vlan_encapsulated_proto;
+ }
  }
 
  if (h_proto == htons(ETH_P_IP))